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Probing Active Galactic Nuclei with ALMA: Advancements in Cosmology and Extragalactic Astronomy

Explore the capabilities of ALMA in unraveling the mysteries of AGN, including resolving obscured molecular tori and studying jet physical properties. ALMA offers unprecedented sensitivity and resolution, enabling in-depth studies of AGN phenomena.

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Probing Active Galactic Nuclei with ALMA: Advancements in Cosmology and Extragalactic Astronomy

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  1. …and AGN Marcello Giroletti Dipartimento di Astronomia, UniBO Istituto di Radioastronomia, INAF

  2. Active Galactic Nuclei ALMA --> Science with ALMA --> Cosmology & Extragalactic Astronomy --> Active Galactic Nuclei AGN can be studied "in depth", because of the low synchrotron and dust opacity and the unprecedented angular resolution of millimeter VLBI. The ALMA will provide millijansky VLBI sensitivity, corresponding to brightness temperatures as low as 100-10000 K. The optically-obscured molecular tori and the circumnuclear starbursts of nearby galaxies can be resolved. The presence of central black holes can be studied kinematically in a large number of galaxies. (from http://www.eso.org/projects/alma/science/cosmo.html)

  3. mm- VLBI ALMA ALMA frequency and resolution

  4. The central engine of AGN • New possibilities opened by ALMA • Study jet physical properties and production mechanisms • Discover new classes of AGN, youngest objects • Observations of the galactic center • Structure of the torus and ISM in the vicinity of the AGN • operating as • independent interferometer • most sensitive element of a mm-VLBI array

  5. Nuclei of radio loud AGN • mm and sub-mm observations can probe • closer to the base of the jet than any other waveband except X-ray • much closer than cm observations because synchrotron self-absorption opacities are lower • monitoring of variability and polarization of thousand of blazars • study correlation between mm and g-ray flares • derive time lags • linear/quadratic, SSC/IC

  6. (Ly et al. 2004) As mm-VLBI element • hundreds of possible targets • not only brightest/closest/most peculiar • see jet collimation region • acceleration/deceleration • velocity structures • relation to other wavelenghts • may even include ARISE (90 GHz, 30 m, space VLBI)

  7. The youngest AGN? • compact symmetric objects are YOUNG • anticorrelation between linear size and turnover frequency • high frequency surveys are expected to detect newly born AGN • stand-alone and mm-VLBI follow ups can constrain formation mechanisms and rates of expansion • expect the unexpected… (O’Dea 1998)

  8. mm-VLBI observations of SgrA* General Relativity calculation VLBI at 1.3 mm VLBI at 0.6 mm maximally rotating BH non rotating BH (Falcke et al. 2000)

  9. Molecular gas around AGN • molecular lines such as 12CO (J=2-1) are good tracers of gas mass in the torus (cold, dense, clumpy) • confirm unified models • separate AGN/starbursts • study inhomogeneities • interactions between jet and ISM • probe physical and chemical conditions at unmatched resolution (Wada & Tomisaka 2004)

  10. Conclusions • ALMA can be most fruitful also for AGN study • high frequency: low opacity, cores & young sources (HFP) • sensitivity: surveys and monitoring • lines: condition of the ISM surrounding the central engine • mm-VLBI • is already feasible • will yield resolution better than any other astronomical instrument ever • will shed light on the vicinity of SMBHs

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